Paper manufacture



May l, 1934 J. H. SWAN, 3D

PAPER. MANUFACTURE 2 Sheets-Sheet 1 INVENTUR ATTORNEY Filed'Aug. 30 1929May 1, 1934. J. H. SWAN, 3D

PAPER MANUFACTURE Filed Aug. 5O 1929 2 Sheets-Sheet 2 INVENTOR A TTORNEY5 fiatented May 1, 1934 UNITED sures PAPER MANUFAfiTURE Joseph H. Swan,3d, Middletown, Ohio, assignor to The Gardner-Richardson ilompany,Middletown, Ohio, a corporation of Ohio Application August 30, 1929,Serial No. 389,424

8 Claims. (01. 91-68) This invention'relates to the manufacture ofpaper, and particularly to the manufacture of board adapted for use inthe tainers and the like.

One of the principal objects of this invention is to provide a paper orboard which is grease proof and moisture proof, is sufiiciently flexibleand elastic to permit bending, is substantially odorless and tasteless,stands up well in use and does not objectionably deteriorate on standingfor considerable intervals'of time, and is commercially economical.

Another object of the invention is to provide a methodof forming such agrease'proof paper or board, which is simple; economical and highlyeffective, and which permits the continuous application of a compositecoating with the formation of a product of good character.

Still another object of the invention is to provide an apparatus forcarrying out the above method.

Other objects and advantages of the invention will be apparent from thefollowing description, from the accompanying drawings and appendedclaims.

In the drawings in'which'like characters of reference designate likeparts throughout the'several views thereof,-

Fig. 1 is a partial diagrammatic side elevational view of apparatusconstructed-for carrying out the method of this invention;

Fig. 2 is a view similar to Fig. 1 disclosing another portion of theapparatus;

Fig. 3 is a plan view of the apparatus shown iii-Fig. 1, certain partsbeing broken away and in section to illustrate the construction thereof;

Fig. 4 is a vertical sectional view taken on the plane of the line 44 ofFig.2; and

Fig. 5 is a vertical sectional View on an enlarged scale of a containerboard made in accordance with this invention.

This invention is particularly applicable to the rendering of paper orboard, such as container board, impervious to grease so that containersmade therefrom may be used for packaging greasy or oily substances whichwould otherwise penetrate through the package. When such a product isused for packaging foodstuffs, it is particularly desirable that thesurface of the container board be substantially tasteless and odorless.The coating should be of such characher as to form an impervious layeron the surface of the board without pin holes which destroy theeffectiveness of the coating, and it should be sufi'iciently flexibleand elastic to permit bending making of con-.

of the board, such as is necessary in the formation of the box orcontainer, Without cracking. The coating should also be of a durablenature and one that will stand up well in use and will not objectionablydeteriorate upon standing for considerable intervals of time. Inaccordance with the present invention, a coated paper product is formedwhich is unusually eflicacious in satisfying the above requirements.

Referring to the drawings which disclose a preferred embodiment ofapparatus constructed in accordance with this invention, a roll of paperto be coated is indicated at 10 carried by asuit able reel which isjournaled at 11 upon a framework 12. The paper to be coated passes in atravelling web indicated at 13 over suitable guide rolls 14 and 15 andthence passes in, contact with the upper surface of roll 16 of a coatingpress. This coating press comprises also a lower roll 17 dipping withina trough 18 to which the coating solution is uniformly supplied in anysuitable manner. Rolls 16 and 17 are positively driven, and are mountedin adjustable bearings so that they can be vertically adjustedrelatively to each otherso as to contact at the nip with the desiredpressure. In operation, rotation of the lower roll 17 within the coatingsolution serves to pick up a film of the coating material upon thesurface of the roll. A portion of this film is transferred to thesurface of the upper roll 16, the amount or thickness of the film beingregulated by adjusting the pressure of contact of the rolls 16 and 17,and this film is then transferred to the travelling web 13.

The coating composition applied at this point comprises a rubber latex,a water solution of an oil insoluble adhesive such as sodium silicate,and an alkaline compound such as ammonia or sodium hydroxide adapted tomaintain the coating in an alkaline condition. The rubber latex is arelatively concentrated water solution or emulsion of the pure sap ofthe rubber tree in colloidal state. The addition of an oil insolubleadhesive, such as sodium silicate, to the rubber latex imparts superiorcharacteristics of adhesiveness, thereby providing an excellent composi-5 or fish glues or gelatine, may be used for this J viously describedand purpose. Other alkali metal silicates suchas potassium silicate canbe used in place of sodium silicate; but from the standpoint of economythe latter is preferred. The presence of an alkali in the coatingprevents deterioration of the same on standing and serves toincrease theeffective life of the coating;

the oil insoluble adhesive is made up in a relatively concentratedsolution. Thus where sodium silicate is used, a. water solutioncontaining in excess of about 20% sodium silicate is preferred.Satisfactory results may be securedwitha solution containing from about15% to sodium silicateby weight. The alkaline compound suchv as ammoniais added to either the rubber latex or the sodium silicateorboth; andthe solutions are then mixed. Satisfactory results have been securedwith compositions containing from 10% to by volume of latex, the balancebeing primarily a water solution of sodiumsilicate of the abovestrength, this composition containing about 1% to 2% by weight on thetotal solids of an alkalinecompound adapted to preserve the alkalinityof the coating- 'Where the coating is used for a lower or base coat itis found preferable to provide in excess of 50% rubber latex by volumein order to give a base coating which has high flexibility and coveringpower.

As an example of a very satisfactory coating composition for the basecoat which is applied to the paper or board, the following is mentioned:Sodium silicate solution of about "38% strength, and rubber latexcontaining about 38% by weight of rubber hydrocarbons and the balancewater and ammonia, are mixed in about 60% or more by volume of rubberlatex and 40% or less by volume of sodium silicate solution to form theliquid coating composition.

In accordance with the present invention, a composite grease proofingcoating is provided on the surface of the, paper or board, whichcomposite coating is made up of upper andv lower coats having differentcharacteristics and which are found to combine to give a superiorresultant coating. bility and the upper coating provides highgreaseproofness and moistureproofness, the composite coating resultingin a very satisfactory greaseproof and moistureproof sheet which can beformed on a forming machine for manufacture into containers or the like.

The web 13with the coating applied to the undersurface thereof at thecoating press 1617 then passes with the uncoated surface in contact withthe guide roll 20, and thence with the coated surface in contact withthe surface of upper roll 21 of a second coating press. This coatingpress is constructed similarly to thecoating press prehas a lowerrotatable roll 22 dipping within trough 23,'whereby a film of coating ofthe desired thickness is transferred from the lower roll 22 to the upperroll 21 and thence to the previously coated surface of the travellingweb 13.

The upper layer of the composite grease proofing coating applied at thispoint comprises a polyliydric alcohol. such as glycerine, an oilinsoluble adhesive such as sodium silicate, and a suitable binder.

the proportions of The lower coating provides high flexi-' The oilinsoiuble adhesive, such as sodium silicate, has high grease proofingqualities, and also assists in securely binding the coating to thesheet. The addition-ofgglycerine to the sodium silicate impartscharacteristics of resiliency to the upper coating and tends to preventcracking thereof when the board is bent in the formation of thecontainer without impairing the greaseproofing character thereof, andalso improves the spreading and covering power of the coating. Otherpolyhydric alcohols, for example glycols such as ethylene glycol, can beused 1 .fwith satisfactory results'in substantially the same In thepreparation 'of the coating composition,

silicate is preferably incorporated a binder, such for example as anoxidized starch, starch acetate or ground talc, flour, chalk and thelike. A water soluble starch compound. such as an oxidized starch orstarch acetate, are preferred due to ease of handling and superiority ofresults. Such starch compounds may be formed into a water solution andthen added to the coating composition to provide a uniformandfree-fiowing coating which is readily applied at the coating press.Such a binder is found to improve the top coating, to make it moredurable, and to prevent the possibility of the coating flaking in a dryatmosphere. In the preparation of the coating composition for this topcoat, the alkali metal silicate is made up in a relatively concentratedwater solution as is the case withthe base coat above described. Theoxidized starch isalso made up into a suitable water solution by heatingthe starch compound in water such as by the introduction of steam.Satisfactory results have been secured with compositions'containing from15% to 40% by volume of glycerine, the balance being made up of a watersolution of sodium silicate and the binder.

As an example of a very satisfactory coating composition for "the uppercoat, the following is mentioned: Sodium silicate solution of about 38%strength is mixed with glycerine and an oxidized starch solution in-theproportions by volume of about 35% sodium silicate solution, 20%glycerine, and 45% starch solution containing'about one pound of thesoluble starch compound to a gallon of water.

The composite. grease proofing coating thus produced has superiorcharacteristics toa ,coatto prevent the upper layer or coat from sinkinginto the sheet. The base coat provides unusual flexibility which isquite important in container board which is subjected to severe bendingin the manufacture of the ultimate containers. This coating forming aflexible background for the overcoat, thus assists in-preventingcracking of the overcoat upon bending of the board. The highpercentageof a rubber compound such as rubber latex in the base coat acts as awater proofing and moisture proofing agent; and the spreading orcovering power of this material together with its flexibility enables asubstantially impervious coating to be formed with only a relativelythin, film. This is materially assisted by the fuzz laying'quality ofthe base coating. The upper layer or overcoat acts as a deodorizer ofthe base vcoat, and fills in any pores'or pin holes which may have beenleft by the base coating. The relatively high percentage of the oilinsoluble adhesive, such as sodium silicate, gives an overcoat havinghigh grease proofing qualities.

As many coatings as desired may be applied to the traveling web 13. Thusas shown, a third coating press comprising an upper roll 28 and a lowerroll 29 dipping within a trough 30 is provided. If it is desired toapply only two grease proofing coats as above described, coatingsolution is not supplied to the trough 30. For the purpose of drying thecoated web, drying blasts such as hot air blasts, are supplied to thecoated surface of the web. As shown, a conduit 32 extends longitudinallybeneath the coating machine from a point somewhat in advance of thefirst coating press to a point sufficiently removed therefrom to securethe proper drying of the web. This conduit is supplied with a dryingfluid such as air by means of a pump indicated diagrammat-' ically at33, the pump forcing air under pressure over suitable heating coils 34.

Intermediate the respective coating presses are upstanding ducts 35 and36 which serve to direct blasts of the heated air against the travelingweb so as to dry the coating sufliciently to permit the next coat to beapplied. The duct 35 discharges the heated air against the web oppositethe area at which the web is supported against guide roll 20, while theduct 36 discharges against the web at the area where it is supported byguide roll 3'7. This arrangement gives the proper tensioning and surfacecontact of the web at the coating presses and also serves to support theweb and hold it adjacent the discharge of the ducts .to securesatisfactory drying while minimizing danger of breaking the web. Beyondthe coating presses a plurality of upstanding extending ducts 38 areprovided which branch off from the conduit 32.

Each of the ducts 35, 36 and 38 is constructed similarly to that shownmore particularly in Fig. 4. The conduit 32 is provided with arectangular opening 39 over which is mounted the respective duct, theend walls of which diverge as indicated at 40 so that an upper outletopening'41 is provided which extends across the full widthof the web.The openings 39 in the respective ducts progressively increase in crosssection from the duct 35 throughout the series to the duct at the end ofthe conduit 32 to thereby equalize the distribution of air dischargedfrom the respective ducts. The duct closest to the pump 33 and at thepoint along the conduit 32 where the pressure is highest thus has thesmallest effective opening,

.and the ducts farther along have progressively supported above thedischarge ports of the various ducts to subsequent treating apparatus;The pressure fluid notonly serves to dry the web during itstravel butalso sustains it suitably spaced from the discharge of the ducts so thatthe coated side of the web does not contact with solid objects untilitis substantially dry. The upper ends of each of the ducts are providedwith a flat rim or flange 46 of smooth metal so as to provide'a undergrease proof coating and to provide a substantially odorless andtasteless outer surface. Very satisfactory results are secured withparaffin, beeswax, montan wax, or other well known in soluble waxes.From the standpoint of economy and ease of application parafiin ispreferred for this purpose. The overlying wax coat not only protects theunder grease proofing coat from exposure and deterioration, but alsoadds to the water proofness and moisture proofness of the coating, whichis particularly advantageous in the packaging of deliquescentsubstances, such as crackers for example.

For the purpose of applying the top wax coat a coating press ispositioned beyond the driers. This coating press comprises an upperrotatable roll 50 and a lower rotatable roll 51, the rolls being mountedin bearings which are vertically adjustable in a suitable frame work 52so as to adjust the pressure of contact at the nip. The web 13 passesdirectly through the nip of rolls 50 and 51 with the undercoated surfacein contact with the surface of roll 51 which in turn 'ps within asuitable trough 53 provided in the rame work 52. This trough may besupplied with a paraffin size solution, or may be supplied with paraflinor other wax which is maintained in a molten condition by suitableheating coils. Rotation of rolls 50 and 51 causes a thin film ofparaffin to be picked up on the surface of roll 51 and thus transferredto the coated web, the thickness of the film being limited by thepressure at the nip.

The presence of a suitable binder, such as a soluble starch compound, inthe top layer of the grease proof coating causes the top paraffin coatto adhere firmly to the coated web. The use of such a binder has afurther advantage in assisting in the control of the amount of parafiinor other wax which is taken up by the sheet during the application ofthis top wax coat. Thus it is found that the higher the percentage ofsoluble starch in the upper layer of the grease proofing coating, themore parafiin the sheet will take for the same roll pressure at the nip,and vice versa.

press through pressure rolls 55 and 56 carried in vertically adjustablebearings by the frame 52. These rolls are preferably constructed in themanner of calender rolls and are steam heated. A high degree of pressureis used at these rolls, and the pressure together with heat serves torender the top wax coat fiuid and spread it uniformly over the surfaceof the coated paper. The pressure roll's 5556 also serve as a drivingmeans for drawing the paper through the machine. The coated paper thanpasses to further treating apparatus, or is wound upon a reel 57, or maybe passed to suitable cutters and cut into sheets of desired size forthe manufacture of containers.

If desired, the paper or board previous to the coating as abovedescribed. maybe first subjected to a sizing treatment. The sizingtreatment is useful in that it tends to prevent curling of the droptest, which means that water will not penetratethe sheet at'that time,is satisfactory. Or the sheet may be given a surface sizing by anapplication of a size to the surface of the formed web, using suitableconventional sizing materials such as above specified. The surfacesizing may be applied during the formation of the sheet prior to theapplication of the grease proofing coating. The sized paper is thensupplied in roll form as indicated at 10 to the coating machine and thegrease proofing coating is applied to the sized sheet.

- Referring to Fig. 5, a section through a preferred sheet or board isdisclosedwhich is found to be highly efiective for use in containers forthe packaging of greasy materials, and which protects the materials fromwater and damp atmospheric conditions. The sheet comprises inner layersof ordinary board stock 60, with an intermediate layer 61 of asphaltmaterial, such as an emulsion of asphalt and clay. The outer surfaces ofthe board are formed of good grade liner stock, there being abottom-liner 62 and a top liner 63. One of the outside liners, such asthe top liner 63, which is adaptedto form the interior of the containerand to receive the grease proof coating, may be a hard sized sheet.

This board as above described may be formed on a conventional cylindermold machine having a number of molds to form the various layers orplies of the sheet, these plies being brought together and united in theordinary manner. Thus a conveying felt of the forming machine passesfirst across a cylinder mold containing the bottom liner stock and formsa web, and then passes successively across cylinder molds provided withboard stock, asphalt emulsion, board stock, and finally top liner stockto form the complete builtup sheet of container board. The board as thusformed is then passed to the coating machine where the composite greaseproofing coating is applied, there being a lower or base coat of highflexibility-indicated at 64 and an upper or overcoat of high greaseproofing quality indicated at .65. A final overlyingwater insoluble waxcoat 66 is then applied over the grease proofing coating. A containerformed from this sheet is protected from water and moisture tending topenetrate from the outside into the interior of the container by theintermediate asphalt layer and by the base coat 64, and is madeeffectively grease proof, water proof and moisture proof on the interiorby the coating applied to the interior surface of the container.

While the forms constitute preferred embodiments thereof, it is to beunderstood that the'invention is not limited to these precise forms, andthat changesmay be made therein without departing from the scope of theinvention which is defined in the appended claims.

What is claimed is:

1. A paper product of the character described comprising a sheet havinga composite greaseproofing surface, said sheet and composite surfacebeing flexible to maintain the continuity of said surface materialagainst disruptive effects I ,to bending and the of inventiwn disclosedherein during use, said surface comprising a lower layer includingrubber latex and anoil insoluble adhesive, an upper layer including anoil insoluble adhesive and a binder, and an overlying top coat of awater insoluble wax, the binder being of such character as to modify theretention and adhering properties of the coated sheet for the waterinsoluble wax.

2. A paper product of the character described comprising a sheet havinga composite greaseproofing surface applied thereto, said greaseproofingsurface comprising a lower layer having high flexibility and includingrubber latex and an alkali metal silicate, and an upper layer havinghigh greaseproofness and including a polyhydric alcohol and an alkalimetal silicate, said sheet and composite coating being flexible tomaintain the continuity ofsaid composite coating against disruptiveeffects in use due to bending and. the like.

3. A paper product of the character described comprising a sheet havinga composite greaseproofing surface applied thereto, said greaseproofingsurface comprising a lower coat which isthe dried deposit of a solutioncontaining in excess 'of 50% rubber latex by volume, the balance beingprimarily a water solution of an alkali metal silicate of a strength inexcess of 20%; and. an upper coat which is the dried deposit of a so-'lution containing in excess of 15% by volume of glycerine, the balancehaving a substantial pro portion by volume of a water solution of analkali metal silicate of a strength in excess of 26%, said sheet andcomposite coating being flexible to maintain the continuity of saidcomposite coating against disruptive efiects in use due to bend! ing andthe like.

4. A paper product adapted for formation into containers comprising asheet having a composite greaseproofing surface applied thereto capableof withstanding bending operations *incident to formation intocontainers without destruction of the impervious character of saidsurface, said greaseproofing surface comprising a lower layer of highflexibility including a rubber material,

coating layer of high greaseproofcomprising a lower layer of highflexibility ineluding a rubber material,

and an upper coating layer of high greaseproofness comprising apolyhydric alcohol, an oil insoluble adhesive, and a binder, said sheetand compositecoating being flexible to maintain posite coating againstdisruptive effects in use due like.

alcohol and a soluble the continuity of said com- 6. A paper product ofthe character described comprising a sheet having a compositegreaseproofing surface applied thereto, proofing surface comprising alower layer of high flexibility including a rubber material, and anupper coating layer of high greaseproofness in-' cluding a polyhydricalcohol, an alkali metal silicate, and a soluble starch compound,saidsheet and composite coating being flexible to maintain thecontinuity of said composite coating against said greasedisruptiveeffects in use due to bending and the like.

'1. A paper product of the character described comprising a sheet havinga composite greaseproofing surface" applied thereto, said greaseproofingsurf ace comprising a lower layer of high flexibility including a rubbermaterial, and an upper coating layer of high greaseproofness including"an alkali metal silicate and a soluble starch compound, said sheet andcomposite coating being flexible to maintain the continuity of ,''saidcomposite coating against disruptive efiects in use due to bending andthe like.

8. A paper product of the character described comprising a sheet havinga composite grease-

